Resources – Who can survive where?
In ecology, the definition of a resource is simply anything which can be used up. This includes food and water, places to live such as burrows or tree hollows, or even just space to grow, like for plants. What resources are important for which animals can depend on a lot of different factors.
There are three ways of getting food; decomposition, parasitism, or predation.
Decomposition feeders eat plants or animals which are already dead and are breaking down. This group includes fungi, bacteria, and animals such as vultures. Not the most appealing idea, but we should really be grateful for them – if they didn’t go around cleaning up, the rotting remains would just sit around making the place unpleasant.
Parasites cheat by stealing food a host animal or plant has already found, and include all sorts of charming creatures, such as worms which live inside the stomach and absorb food around them which their host has already found and eaten.
Predators get their food by eating other organisms. In ecology, this includes carnivores AND herbivores. We usually think of predation as a lion hunting down a zebra or something similar, but in ecological terms, even a sheep can count as a predator. After all, they eat grass, which is just another living thing doing its best to survive!
Image credit: Sheep by Alistair Young via Flickr (CC BY-SA 2.0)
Specialists vs Generalists
A lot of animals are generalists. This means they can eat a range of different foods and live in more than one type of environment. For instance, cows can eat most types of grass, many types of weeds, and the leaves of lots of trees and bushes. They can live in the cold hills of Scotland, in the rain and the fog, and they can also live on the vast flat stretches of dry country in Australia’s north.
Specialists, on the other hand, can only live in very specific conditions. They usually have a very particular type of food they eat, and/or very particular types of environments they can survive in, often being specially adapted to make use of resources others can’t. For example, koalas have evolved to live exclusively on a few varieties of gum leaves. The leaves don’t give much energy and are difficult to digest, so very few other animals eat them. Koalas manage by having low-energy lifestyles, sleeping for much of the day and having specially adapted digestive systems.
Image credit: Koala by Abbey via Flickr (CC BY-SA 2.0)
The advantage of being a generalist is that you can survive in many different places, whereas specialists are in big trouble if their chosen food runs out, or something happens to their chosen habitat, like a large portion being destroyed. However, as long as their food and habitat is available, specialists have the advantage of facing less competition. Because they’ve adapted to use resources others don’t, they rarely have to race or fight other species to get it. Generalists, on the other hand, face competition every day, as they live on land lots of species can live on, and eat food lots of other species can eat.
Every animal is different, and has different needs, but the way they coexist is vital to the survival of the environment.
For more information: